1. Technical Field
The present invention relates generally to the data processing field and, more particularly, to a method, system and computer program product for monitoring the status of components in a data processing system.
2. Description of Related Art
Java Management Extensions (JMX) application programming interface (API) provides a mechanism for monitoring the status of components, for example, servers, applications, processes and other resources, in a data processing system such as a Java Enterprise Edition (J2EE) server. The status monitoring API requires a user to perform complex queries in order to obtain the status of components and consequently, it is advantageous to provide a simple client which allows a user to visualize the status of large groups of components. Such a client may conveniently comprise a web page containing a series of images corresponding to the states of the various components being monitored.
JMX queries are executed asynchronously and may not be completed within any specific period of time. The content of a web page, however, typically loads and displays serially. Accordingly, a JMX query may not begin until a previous query has been completed. As a result, although many queries may require only a short period of time to complete, other queries may need more time; and one long-running query can block the completion and display of other, shorter queries.
In a known technique for monitoring the status of a plurality of components in a data processing system, a user at a client device, such as a web-based administrative console, initiates JMX queries to determine the status of the components. The queries are first transmitted to a servlet which processes a first query to determine the status of a first component. The first component responds, and the servlet then processes a second query to determine the status of a second component. Only when responses have been received from all of the plurality of components does the servlet provide the responses to a browser running in the client device.
Often, a user is interested in only a subset of the components for which the status is presented, or is interested in information other than or in addition to the status of the components, for example, a simple list of application servers. Because a JMX query can require as much as three minutes to complete, and because the servlet does not provide the responses to any status queries until responses are received from all components, the user may have to wait a substantial period of time to see the responses even though the specific information desired by the user may be available almost immediately.
A copending application entitled “TOOL FOR DISPLAYING JMX MONITORING INFORMATION”, Ser. No. 10/721,819, filed on Nov. 24, 2003, assigned to the same assignee as the present application, and incorporated herein by reference, describes a mechanism that allows the status of data processing system components obtained through JMX queries to be loaded asynchronously in web content such that the status value of each component is displayed as soon as the value becomes available, without having to wait for the completion of any other query. The mechanism uses JMX and specialized images to acquire status information for a large number of components. An image's source attribute is set as a servlet, and the servlet uses JMX to acquire the status of a component, and streams data (corresponding to the appropriate image) back to the browser.
From an accessibility perspective, a problem arises in that the mechanism used by accessible technologies to determine the “value” of an image (i.e., the ALT or TITLE attribute on the image) is not available to the user when the image is streamed back to the browser. This limitation can be overcome by including static content on those attributes that basically say “click” on this image to request text describing the component status. Such a procedure for accessing additional information regarding the status of a component, however, requires opening a new window within which the text for the status is displayed, and is not an optimal solution to the problem.
For non-accessible needs users, such as visually impaired users, dynamic HTML can be used to show a “legend” table that maps images to text for the status. Such an approach, however, is also not fully satisfactory.
It would, accordingly, be advantageous to provide a mechanism for monitoring the status of components in a data processing system that improves the accessibility of JMX monitoring information in web content.